This invention relates to a mechanism for aligning a hand-held power saw, and, more particularly, to a mechanism that allows the saw blade to be aligned at a predetermined position with respect to the edge of the workpiece.
Users of hand-held power saws, and particularly hand-held circular saws, typically have great difficulties aligning the saw blade with the desired cutline on the workpiece. More specifically, most saw users often make cuts that are generally at 90 degrees with respect to a straight edge of the workpiece. Therefore, users often draw or mark a line on the workpiece to indicate the path upon which the blade should pass to obtain a perpendicular cut.
In the past, to begin the cut along the desired cutline, the user would first attempt to align the blade with the line by positioning a guide slot (formed in the planar cutting base of the saw) at the beginning of the line. Because the user had no means to "square" the cutting blade with respect to the workpiece edge, oftentimes the initial cut of the blade was not properly aligned. Once the blade was started in a direction that was divergent from the desired cutline, it was often difficult to correct the direction of the blade. Further, even if the blade could be corrected, the end result was a cut edge that was not planar but which may have had numerous undulations resulting from the blade corrections.
Attempts have been made to provide attachments that allow the saw blade of a circular saw to be squared with the workpiece edge. Most of these aligning structures are very bulky, expensive, cumbersome, and greatly increase the weight of the saw. One such structure is disclosed in U.S. Pat. No. 3,045,724. As is apparent, such a structure greatly impairs the user's ability to position the circular saw in tight surroundings.
An additional type of alignment mechanism is shown in U.S. Pat. No. 4,730,396. This patent discloses one arm pivotally mounted to and extending below the base of a circular saw. A spring urges the arm to an operable position below the saw base. In order to align the saw blade, an operator moves the saw forwardly such that both the saw blade and the arm contact the edge of the workpiece. As the saw is moved further forward, the arm pivots in a rearwardly direction and retracts from its operable position below the bottom of the saw base to a nonoperable position above the bottom of the base.
The aligning mechanism disclosed in this patent is disadvantageous for a number of reasons. First, the alignment system oftentimes results in inaccurate alignment. More specifically, one of the two spaced points that contact the edge of the workpiece is the saw blade. The blade has an uneven periphery in that it presents the peaks and valleys associated with the cutting teeth. Therefore, the alignment of the blade can vary depending upon whether a peak or a valley contacts the workpiece edge. Furthermore, different types of blades can have different tooth configurations and different diameters. As is apparent, the variability in tooth configurations and diameters will also result in inaccurate alignment. A further disadvantage of the saw blade acting as one of the contact points for the edge is that the blade will often mar the edge during the aligning procedure. Thus, the alignment mechanism of the above patent may result in damage to the workpiece.
Therefore, an alignment mechanism is needed which will overcome the problems with the prior art aligning mechanisms discussed above.